1. Field of the Invention
The present invention generally relates to an image scanning apparatus having a full rate carriage with a lamp (light source), and more particularly to an improvement on a harness extending to the lamp from a power supply in such image scanning apparatus.
2. Description of the Related Art
An image scanning apparatus that is combined with an image forming apparatus such as facsimile machines and photocopiers has a scanner adapted to move below a platen (glass), on which a document to be scanned is placed. The scanner can move in a sub-scanning direction. The scanner generally includes a full rate carriage having a lamp and first mirror, and a half rate carriage having second and third mirrors. The half rate carriage follows the full rate carriage at a half speed of the full rate carriage. The lamp is a light source which radiates the document on the platen. The light from the lamp is reflected by the document, and the reflected light is collected to a photoelectric converter such as CCD by the first to third mirrors and lens to transform a light signal to an electric signal. CCD then outputs an image signal (digital signal). This digital signal is used as a facsimile transmission signal. In case of photocopier, this digital signal is sent to a write means in an image recording unit to write a photo-image on a photosensitive body.
In order to feed electricity to the lamp on the full rate carriage, a harness extends to the full rate carriage from a power supply attached to a machine frame, which houses substantially all elements of the image scanning apparatus. High voltage is supplied to the lamp through the harness. In the conventional arrangement, the harness extends outside a scanner frame, which houses or supports the scanner, such that it does not become an obstacle to the two carriages moving below the platen. Referring to FIG. 7 of the accompanying drawings, schematically illustrated is relationship between a scanner 10, harness 25 and machine frame 2 in a plan view. A space 40 should be cleared in a rear area of the machine frame 2 behind a scanner frame 44 in the main scanning direction to accommodate the harness 25. This space 40 makes the machine frame depth (or thickness) large and in turn the machine size large.
An object of the present invention is to cause a lamp harness to extend in a way not to obstruct a light path of a scanner while making a machine depth small.
According to one aspect of the present invention, there is provided an image scanning apparatus having a platen glass on which a document to be scanned is loaded, a scanner which includes a full rate carriage movably located below the platen glass, a light source (lamp) mounted on the full rate carriage for emitting a light to the document on the platen glass, a half rate carriage also located below the platen glass and movable in association with the full rate carriage, a harness for feeding electricity to the light source, and a machine frame for accommodating substantially all elements of the apparatus. The machine frame has a depth in a main scanning direction of the scanner. The light from the light source is reflected by the document, and introduced to a photoelectric converter such as CCD. Thus, the light defines an optical path from the light source to the photoelectric converter below the platen glass. The full and half rate carriages are movable in the sub-scanning or width direction of the machine frame. In the invention, the harness extends within an area defined by the movable zone of the full and half rate carriages, and is guided not to obstruct the optical path of the light. Therefore, a space is not needed behind a scanner frame in the main scanning direction, and the machine frame depth can be reduced.
The image scanning apparatus may further include a turn element, and the harness may extend to the turn element from the full rate carriage such that its direction is turned 180 degrees downward. After the turn element, the harness extends toward a power supply mounted on the machine frame. This turn element may be a harness guide attached to the half rate carriage.
The turn element may be located below the optical path between a first mirror mounted on the full rate carriage and a second mirror mounted on the half rate carriage. The light reflected from the document is incident on the first and second mirrors in turn.
Two pairs of rail may extend along front and rear faces of the machine frame in the sub-scanning direction such that the full rate carriage moves on the first pair of rails and the half rate carriage is moves on the second pairs of rails. In this case, the above-mentioned scanner frame may be defined by the first and second pairs of rails, and the machine frame substantially may overlap the scanner frame if viewed from above. The harness may extend within the first (or second) pair of rails if viewed from above. More specifically, the harness may extend along the rear face of the machine frame, and the optical path may be defined inward of the harness. Mirrors of the full and half rate carriages may cause the optical path to converge inside the machine frame.